| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
CELLULAR |
1 Department of Physiology, New York Medical College, Valhalla, NY 10595, USA
Repetitive synaptic stimulation in the stratum radiatum (SR) evokes large amplitude Ca2+ waves in the thick apical dendrites of hippocampal CA1 pyramidal neurons. These waves are initiated by activation of metabotropic glutamate receptors (mGluRs), which mobilize inositol-1,4,5-trisphospate (IP3) and release Ca2+ from intracellular stores. We explored mechanisms that modulate the spatial properties of these waves. Higher stimulus current evoked waves of increasing spatial extent. Most waves did not propagate through the soma; the majority stopped close to the junction of the soma and apical dendrite. Pairing strong stimulation with one electrode and subthreshold stimulation with another (associative activation) extended the waves distally but failed to extend waves into the cell body. Pairing synaptic stimulation with backpropagating action potentials enhanced the likelihood of wave generation but did not extend the waves to the somatic region. Priming the stores with Ca2+ entry through voltage dependent channels modulated wave properties but did not extend them past the dendrites. These results are consistent with propagation failing due to the dilution of synaptically generated IP3 as it diffuses into the large volume of the soma (impedance mismatch). Synaptically activating waves in the presence of low concentrations of carbachol, which probably increased the tonic level of IP3 throughout the cell, enhanced the extent of propagation and generated waves that invaded the soma, as long as low-affinity indicators were used to detect the [Ca2+]i changes. Consistent with this explanation direct injection of IP3 into the soma promoted wave propagation into this region. Ca2+ waves that propagated through the cell body were interesting because they did not fill the volume of the soma, but passed through the centre, often with large amplitude. These waves may be particularly effective in activating gene expression and protein synthesis.
(Received 25 May 2006;
accepted after revision 26 June 2006;
first published online 29 June 2006)
Corresponding author W. Ross: Department of Physiology, New York Medical College, Valhalla, NY 10595, USA. Email: ross{at}nymc.edu
This article has been cited by other articles:
|
|
 |
|
  J. M. Power and P. Sah Competition between Calcium-Activated K+ Channels Determines Cholinergic Action on Firing Properties of Basolateral Amygdala Projection Neurons J. Neurosci., March 19, 2008; 28(12): 3209 - 3220. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. M. Hagenston, J. S. Fitzpatrick, and M. F. Yeckel MGluR-Mediated Calcium Waves that Invade the Soma Regulate Firing in Layer V Medial Prefrontal Cortical Pyramidal Neurons Cereb Cortex, February 1, 2008; 18(2): 407 - 423. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Hong and W. N. Ross Priming of intracellular calcium stores in rat CA1 pyramidal neurons J. Physiol., October 1, 2007; 584(1): 75 - 87. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M. Power and P. Sah Distribution of IP3-mediated calcium responses and their role in nuclear signalling in rat basolateral amygdala neurons J. Physiol., May 1, 2007; 580(3): 835 - 857. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Cui, B. E. Bernier, M. T. Harnett, and H. Morikawa Differential Regulation of Action Potential- and Metabotropic Glutamate Receptor-Induced Ca2+ Signals by Inositol 1,4,5-Trisphosphate in Dopaminergic Neurons J. Neurosci., April 25, 2007; 27(17): 4776 - 4785. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
